Diesel particulate filter apparatus

Abstract

In this DPF apparatus, the filters have large trapping areas and three-dimensionally and efficiently trap particulates contained in the exhaust gas thereby cleaning the gas and reducing the size of the apparatus. The DPF apparatus has the main filter installed in the case incorporated into the exhaust system, the sub-filter arranged in the central portion of the main filter, and the bypass cylinder interposed between these filters. The bypass valve is installed on the exhaust gas inflow side of the sub-filter to open and close the inflow port of the sub-filter. The main filter and the sub-filter are made from ceramics porous sheet filters, or comprise a nonwoven cloth made of silicon carbide fibers and a woven cloth made of ceramics long fibers chosen from Si-C and Si-C-Ti-O long fibers and arranged adjacent to and downstream of the nonwoven cloth. The mesh heaters are laminated over the main filter on the exhaust gas inflow side.

What is claimed is: 
     
       1. A diesel particulate filter apparatus comprising: a case incorporated in an exhaust system of a diesel engine;   filters installed in the case to trap particulates contained in exhaust gas, the filters comprising a nonwoven cloth made of silicon carbide fibers and a woven cloth made of ceramic long fibers arranged in contact with and at least downstream of the nonwoven cloth with respect to the exhaust gas flow;   mesh heaters arranged in contact with and upstream of the nonwoven cloth with respect to the exhaust gas flow, the mesh heaters being supplied with electricity to heat and burn particulates trapped in the filters; and   a fixing member for firmly holding together the nonwoven cloth, the woven cloth and the mesh heaters.   
     
     
       2. A diesel particulate filter apparatus according to claim 1, wherein the ceramic long fibers forming the woven cloth are selected from long fibers of Si-C and Si-C-Ti-O. 
     
     
       3. A diesel particulate filter apparatus according to claim 1, wherein the woven cloth comprises a first woven cloth located upstream of the nonwoven cloth with respect to the exhaust gas flow and a second woven cloth located downstream of the nonwoven cloth with respect to the exhaust gas flow, and wherein gaps between the fibers of the first woven cloth are coarser than those of the second woven cloth. 
     
     
       4. A diesel particulate filter apparatus according to claim 3, wherein the mesh heaters are interposed between the nonwoven cloth and the first woven cloth. 
     
     
       5. A diesel particulate filter apparatus according to claim 1, wherein the mesh heaters comprise heat-resistant steel wires containing Ni-Cr and the surfaces of the mesh heaters are coated with a nonconductive material of Al 2  O 3 . 
     
     
       6. A diesel particulate filter apparatus according to claim 19, wherein the heat-resistant steel wires attached to the surface of the mesh heaters are coated with Al 2  O 3 .